Posts: 203
Threads: 29
Joined: Nov 2009
Ouch! The previous owner, a college prof., said he ran it for years on the A/C alone. I guess I'm off to e-bay to find a battery pack. I did get what looks to be an external battery charger with the deal.
Thanks for the warning. It would be shame to fry my new baby.
Posts: 875
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Joined: Jul 2005
It can certainly do no harm to only use the adapter/charger with a battery installed, but I do not believe there is any danger at all in powering the 45 (or the 35, 55, 70 or 80 models) directly from the AC adapter/charger with no battery in the calculator. The AC adapter/charger used on the 45 provides a regulated supply voltage to power the calculator. When the connector is plugged into the calculator, the calculator’s internals get connected directly to the regulated supply from the AC adapter/charger. The battery gets completely disconnected from the calculator's internal circuitry and is connected to the variable-voltage charging output of the AC adapter/charger. Page 48 of the HP-45 manual discussed what to do if your battery pack went bad, stating "Remember, you can use your HP-45 on AC power until the replacement battery pack arrives.”
This does not apply to the HP-65 or HP-67 which use the same charger, but (if I recall correctly) leave the card reader circuitry connected to the battery and the variable voltage charging supply, so if there is no battery that voltage jumps up to something like 17 Volts which could damage things.
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